Building tree like structure for feeding Freemarker from JDBC - jdbc

Question

I want to generate code with Groovy and Freemarker (especially GFreeMarker) - I want to generate a Java wrapper for calling stored procedures. So I query ORACLE with this statement:
select PACKAGE_NAME, OBJECT_NAME, POSITION, ARGUMENT_NAME, DATA_TYPE, IN_OUT
from USER_ARGUMENTS
This data is denormalized (each parameter is on a line) and hierarchical:
- Package (PACKAGE_NAME)
- Function (OBJECT_NAME)
- Arguments (ARGUMENT_NAME, DATA_TYPE, IN_OUT)
I want to store it into an hierarchical structure to feed it to Freemarker to generate code. This means that for every row I have to create a new Package instance or select an existing on, then create a new Function instance or select an existing one and create a new argument.
Can this be done via an ObjectGraphBuilder or should I go into a combination with maps and lists?
How is this done in a "groovy way"? Thanks for your help!

Answer 1

Groovy or not, I did it the following way, please provide better answers and I will accept it!
First I build the following structure:
Map packages = new LinkedHashMap()
class Package {
String name
Map functions = [:]
}
class Function {
String name
String returnType
boolean isFunction = false
Map parameters = [:]
}
class Parameter {
String name
String dataType
String inOut
}
Then I read it with
sql.eachRow("""\
select PACKAGE_NAME, OBJECT_NAME, POSITION, ARGUMENT_NAME, DATA_TYPE, IN_OUT
from USER_ARGUMENTS
order by PACKAGE_NAME, OBJECT_NAME, POSITION""")
{
// create or get package
def thePackage = packages[it.PACKAGE_NAME ?: '']
if (thePackage == null) {
thePackage = new Package(name : it.PACKAGE_NAME ?: '')
packages[it.PACKAGE_NAME ?: ''] = thePackage
}
// create or get function
def theFunction = thePackage.functions[it.OBJECT_NAME ?: '']
if (theFunction == null) {
theFunction = new Function(name: it.OBJECT_NAME ?: '')
thePackage.functions[it.OBJECT_NAME ?: ''] = theFunction
}
// Position 0 is the return value
if (it.POSITION == 0) {
theFunction.isFunction = true
theFunction.returnType = it.DATA_TYPE
}
else {
// create the argument
def theParameter = new Parameter(
name: it.ARGUMENT_NAME, dataType: it.DATA_TYPE, inOut: it.IN_OUT)
theFunction.parameters[it.ARGUMENT_NAME ?: ''] = theParameter
}
}